Engines may use various forms of fuel delivery to provide a desired amount of fuel for combustion in each cylinder. One type of fuel delivery uses a port injector for each cylinder to deliver fuel to respective cylinders. Still another type of fuel delivery uses a direct injector for each cylinder.
Further, engines have been proposed using more than one type of fuel injection. For example, the papers titled “Calculations of Knock Suppression in Highly Turbocharged Gasoline/Ethanol Engines Using Direct Ethanol Injection” and “Direct Injection Ethanol Boosted Gasoline Engine Biofuel Leveraging for Cost Effective Reduction of Oil Dependence and CO2 Emissions” by Heywood et al. are one example. Specifically, the Heywood et al. papers describe directly injecting ethanol to improve charge cooling effects, while relying on port injected gasoline for providing the majority of combusted fuel over a drive cycle. The ethanol provides increased octane and increased charge cooling due to its higher heat of vaporization compared with gasoline, thereby reducing knock limits on boosting and/or compression ratio. Further, water may be mixed with ethanol and/or used as an alternative to ethanol. The above approaches purport to improve engine fuel economy and increase utilization of renewable fuels.
However, the inventors herein have recognized several issues with such an approach. Specifically, requiring a user to always provide separate fuels (e.g., gasoline and ethanol) can be burdensome to the operator. To simplify use of an engine with more than one type of fuel injection, the inventors herein have recognized that such an approach may be more easily implemented by the use of an apparatus having an extractor disposed between a fuel tank and internal combustion engine, and by the use of a method of operating the apparatus comprising adding a volume of a mixed fuel into the extractor from the fuel tank, wherein the mixed fuel contains at least one substantially nonpolar fuel component and at least one polar fuel component, adding a volume of a polar solvent to the extractor, extracting at least a portion of the polar fuel from the mixed fuel into the polar solvent, thereby forming a first fuel mixture with an enriched concentration of the polar fuel and a second fuel mixture with a reduced concentration of the polar fuel, and providing the first fuel mixture and the second fuel mixture to the engine in a ratio selected based upon engine operating conditions. This approach takes advantage of already available gas/alcohol mixtures, and therefore may allow advantages of multiple injection and/or multiple fuel strategies to be employed without inconveniencing a user. Furthermore, in some embodiments where water is used as the polar solvent, the presence of water in the first fuel mixture may allow the second fuel mixture to be used for charge cooling to help prevent pre-ignition. These and other advantages are discussed in further detail below.